From L unus came the abstract noun unitas (“oneness”), whence E unity. There was a Latin synonym unio, source of E union—and, believe it or not, of onion. L unicus gave us unique. The Latin noun quadra (“square”) clearly shows its numerical origin; English square, squad, and squadron are all well disguised derivatives of vulgar Latin *exquadra. The poet Horace popularized the term sesquipedalian, used humorously to describe words “one and a half feet” in length. Number systems based on twelve are called duodecimal, from L duodecem (12), ultimate source of E dozen, a French transmission. (Only a mischievous librarian would claim that duodecimal is related to Dewey Decimal.)
It is perhaps confusing that English forms in tri- may be from either Latin or Greek. Some Latin derivatives include triangle, tricolor, triennium, trimester (3 months), trisect, and triumvirate. A bang-up Latin “tri-” word is TNT (tri-nitro-toluene = C7H5N3O6). Greek derivatives in English include trilogy, trimeter, tripod, triptych, trilobite (a Palaeozoic fossil with 3 lobes), and triceratops (tri-cerat-ops < τρι- + κερας, κερατ-ος, “horn” + ὀψ, “face”)—one of many familiar dinosaurs to bear a thoroughly Greek name.
SPECIAL NOTE: The next two sections (§128 and §129) are inserted for those who are curious to explore the nomenclature of the metric system and other specialized aspects of numerical terminology. The two sections are intended for reference only. Readers with less interest in these matters may skip immediately to §130.
- E dinosaur < modern Latin dinosaurus < G δεινος (“terrible”) + σαυρος (“lizard”). ↵